Newbie here doing a 20.8kW DYI install (80 sunMAX 260W panels with microinverters)

[bcroe]

Bruce, very interesting concept of wiring 2 panels in parallel with one facing East and the other West. As
the cost of panels continue to drop, I can see that more people going for that, especially if they have limited mounting options.

They say the panels only represent 1/4 of a systems cost. Obviously this method will out perform a tracker. I got tired of seeing my
equipment doing very little under the cloudy skies of northern ILL. With the extra panels the cloudy day output is way up, and with
proper orientation the sunny days have more useful hours. Here are curves I ran with 1 + 3 indicating power on a sunny day
for a pair of E-W panels. 60 degrees elevation seems to be about right: less gives too big a mid day peak; more gives a big drop mid
day. Actual results are 50% more energy than your estimates. Every situation is different; run your own simulations and see. Bruce Roe

[tyab]

Previously I posted about IronRidge system for possibly using some of your ground - here are some photos that we did over the weekend.

http://solargroundmount.blogspot.com/

[pclausen]

Very cool Bruce. Yeah, that would be the way to go if you allowed peak output is limited (by the State in my case).

tyab, looks like you made some great progress over the weekend!

I spoke to J.T. at Ironridge today, he added the SunMAX panels to their online configurator and I'm working with Renvu on a quote. So 54 panels will go on the shop roof and the remaining 24 will be ground mount, split into 2 sections given my East West elevation change.

FedEx freight called this afternoon, they will be bringing my system out on Wednesday. 4 skids in all.

[tyab]

Sounds like you are moving right along. So far I have no issues with the IronRidge system. For the pipe - just source it locally. IronRidge talks about the option of using mechanical tubing but I just went with standard schedule 40 pipe since it was easy to get. I should have rails up later this week so I'll get some good closeups of those parts and how I am attaching the AC combiner boxes. One thing I forgot to mention on the blog was I used some aluminum anti-oxide on the inside walls of those caps where there would be contact with the pipe but that cap looks like it already has some sort of coating on it for oxide prevention.

[pclausen]

Definitely keep us posted on how the IronRidge works out. My panels, microinverters and mounting hardware showed up today. Took up an entire bay in my shop!

[tyab]

Nice photos - my garage has looked like that all summer (ordered the stuff way too early).

Hey - I saw in your design that you are using 1/2" PVC on roof and 1" PVC down. PVC on roof gets hot and that 1/2" can really sag, make sure you are familiar with NEC article 352 and in particular 352.44. Short version, for most areas of the country, once you have an exposed outside run of PVC near/over 6' you need to think about expansion joints. Originally I was planning on PVC above ground but switched to EMT partily to avoid those expansion issues. Also for those conductors in the conduit don't forget to review the wire adjustment factors in 310.15(B)(3)

[pclausen]

Thanks for the NEC references. Good reads for sure. Based on what you said about PVC on the roof and other testimonials I found, I'll do EMT instead. Everything else inside my shop is EMT, and I already have a bender, so might as well stick with that. Need to look into what water tight fittings I'll need. The end runs on my strings feature 1/2" NPT threads, so I figured something like this would work (taped of course):

[tyab]

For outdoors EMT all fittings must be raintight. They are available just about everywhere. These are the ones I am using:

http://www.aifittings.com/catalog/emt/emt-rain-tight-compression-connectors-with-insulated-throat/

The term "Insulated throat" means that they have a smooth nylon insert in the body end so there are no edges for the wire to scrap on. They are required for #4 wire and larger - 300.4(G) - but I'm using them on all conduit - the cost difference is minimal.

EMT is covered under NEC article 358. Main things, ream all cut ends and no threading - must use fittings 358.28, fasten within 3 ft of a junction box and support every 10 ft 358.30

[pclausen]

Thanks. If I stick with EMT, I'll definitely use those. It has been suggested I can use flexible conduit between between the End Runs and the bass through box. They make both metallic and non-metallic. That would be a whole lot easier to work with than EMT. Everything would be below the panels, so direct sunlight would not be an issue, although that stuff is UV resistant from what I read.

I did make some decent progress over the weekend. I got all my fasteners installed on the roof:



And I got the front trim panels up as well:



And I have a couple of 1" expansion gaps along the way.



Did manage to get the first 2 panels up last night after work.





Only 54 panels to go, lol.

[Robert1234]

Very cool, and we're much at the same point. All my fasteners are up. You are ahead of me by front rail and 2 panels right now lol. I'm not DIY this time though. Once is all the fun I can handle

P.S. You are moving along pretty quick. Impressive.

[pclausen]

Also for those conductors in the conduit don't forget to review the wire adjustment factors in 310.15(B)(3)

In my case I will have 8 current carrying conductors (4 strings with L1 and L2), 4 Neutrals and a single ground, for a grand total of 13 wires. All are going to be #10. Looking at a fill chart for 1" PVC Conduit Sch 40, I'm allowed 15 #10 wire in a 1" pipe. However, once taking 310.15(B)(3) into account, it looks like I need to reduce the count to 70%, or 10 wires. So it appears that I need to up the conduit down to the panel to 1 1/4", which allows for 27 #10 wires. 70% of that is 18 #10 wires, so I should be in good shape. Heck, I could even run the 4 individual grounds all the way down to the breaker panel if I wanted and not have a single splice in the pass through box. Do I have that right?

[DanS26]

Previously I posted about IronRidge system for possibly using some of your ground - here are some photos that we did over the weekend.

http://solargroundmount.blogspot.com/

After seeing Jack's Solar Ground Mount Journal, I'd thought I'd pass along to future ground mount DIY'ers a better, faster, cheaper and safer way to build a ground mount. Especially if you are building with 3" HEAVY schedule 40 galvanized pipe.

It is not necessary to build those 2x4 framing support members and having a crew of people around to accomplish the ground mount. The pic below shows a method using just one person to properly set and align a ground mount. Here's the method:

Auger the hole to IronRidge specifications....no need for Sonotubes. Square the rectangle by measuring the diagonals BEFORE drilling the holes.
Use crushed stone to set the height of the pipe by adding or subtracting stone in the hole....use a laser level....any good rental outfit will have one
Set the pipes in a row with mason string.
Using a standard carpenter level make the posts perfectly horizontal and vertical with the small adjustment wood pieces as shown in the pic.
Now with everything leveled and square....just pour the concrete.......one person and job is done.

IMG_0282.JPG IMG_0289.JPG IMG_0296.JPG IMG_0355.JPG

[tyab]

You do not have to reduce the number of conductors due to temperature by itself. Lets take your example. I don't know how many panels are on each string but that does not matter, let compute the maximum current allowed by each #10 wire and then you will be able to know if #10 works for you.

Assuming you are running THNN/THWN-2 #10 copper wire - southwire simpull for example. I love this wire and it pulls so easily and Lowes / Home Depot carry it.
This wire is rated for 90C temps both dry and wet. Outdoor conduit is a wet location. So we use the 90C column of 310.15(B)(16) and this wire is rated for 40 amps for an ambient temperature of 86F

That 40 amp rating is assuming that the conduit it will be in is also rated for 90C. PVC is not - it is listed for 50C via 352.12(D). Oops we can't use the 90C table. There is no 50C table so technically we have to use the engineering formula but lets just use the 60C column and looking at the 75C column, lets just take off another 5 amps.

The 60C column for that wire gives 30 amps.
30 amps - 5amps = 25 amps.

Now we derate this wire based on your conductors and temperature.
First lets do temperature.

Lets assume that the historical high where you live is 100F. And being on roof in sunlight the temps can be +40F higher via 310.15(B)(3)(c) so the high is 140F. Use table 310.15(B)(2)(a) and it gives a correction factor of 0.71.
25 amps x 0.71 = 17.75 amps.

Now adjust for number of conductors.
You have 8 current carrying conductors. You ignore the four neutrals and ground via 31015(4) and 310.15(5) (microinverters use the neutral to carrying the unbalanced load).so you have 8 conductors. Table 310.15(b)(3)(a) gives 0.70.
17.75 amps x 0.70 = 12.42 amps.

Thus your #10 is able to able to support 12.42 amps inside of PVC assuming your historical high is 100 so you use the #10 and do not have to increase the conduit size due to having to use larger wire. You don't have to increase conduit size due to temperature - only due to number of wires and the size of the wire.

Now we switch to 690 to make sure that #10 wire is ok for microinverter string. Here you need to know the number of microinverters per string and what is the current limit of the microinverters. I'm going to use the Enphase M250's I am using since the math for them is really easy. Each M250 is current limited to 1 amp output.
Lets say we have 8 microinverters per string, so the output is 8 amps.
We must apply a 125% factor via 690.8(B)(1)
8 amps x 1.25 = 10 amps.

We have already done the adjustment above factors, so the #10 wire with all adjustments supports 12.42 amps and we only need 10 amps so #10 works. The #10 wire will have a 10 amp OCPD (circuit breaker).

[tyab]

When I had my first inspection, my AHJ was very clear with me - nothing in the hole except wet concrete. He went over all the ways that he fails inspections for Iron Ridge setups. No pre-filling and letting concrete harden to give a bed to set the pipe on. The pipe must be suspended in some manner and the bottom of that pipe must be a depth that is a minimum of 2/3 of the hole depth. Nothing should be in the hole for the listed depth except concrete. I showed him the 2x4 supports and described how we are hanging the pipe and he approved it even thou I did not have that part of the foundation setup since he said I was doing it correctly and he agreed we could not setup the supports due to safety issues with all of the ground ring trenches.

But if your AHJ approved that before you poured concrete - hats off to you for an easy setup! I'm jealous.

[DanS26]

When I had my first inspection, my AHJ was very clear with me - nothing in the hole except wet concrete. He went over all the ways that he fails inspections for Iron Ridge setups. No pre-filling and letting concrete harden to give a bed to set the pipe on. The pipe must be suspended in

Ksome manner and the bottom of that pipe must be a depth that is a minimum of 2/3 of the hole depth. Nothing should be in the hole for the listed depth except concrete. I showed him the 2x4 supports and described how we are hanging the pipe and he approved it even thou I did not have that part of the foundation setup since he said I was doing it correctly and he agreed we could not setup the supports due to safety issues with all of the ground ring trenches.

But if your AHJ approved that before you poured concrete - hats off to you for an easy setup! I'm jealous.

I also drilled a hole through the pipe six inches from the bottom, then placed a piece of 5/8 inch x 12 inch piece of rebar horizontally through the pipe. I also made sure that the depth of pipe in concrete exceeded the IronRidge specs.

I used crushed stone in the hole so that accumulated water from condensation, etc could escape thus extending the life of the pipe. Really not necessary since dirt would have worked just as well to level.

I would have questioned your AHJ on his suspended construction requirement. Sometimes that is the only way they have seen it done.